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  • Electronic relaxation mechanism of 9‐methyl‐2,6‐diaminopurine and 2,6‐diaminopurine‐2′‐deoxyribose in solution
Title: Electronic relaxation mechanism of 9‐methyl‐2,6‐diaminopurine and 2,6‐diaminopurine‐2′‐deoxyribose in solution
Abstract Prolonged ultraviolet exposure results in the formation of cyclobutane pyrimidine dimers (CPDs) in RNA. Consequently, prebiotic photolesion repair mechanisms should have played an important role in the maintenance of the structural integrity of primitive nucleic acids. 2,6‐Diaminopurine is a prebiotic nucleobase that repairs CPDs with high efficiency when incorporated into polymers. We investigate the electronic deactivation pathways of 2,6‐diaminopurine‐2′‐deoxyribose and 9‐methyl‐2,6‐diaminopurine in acetonitrile and aqueous solution to shed light on the photophysical and excited state properties of the 2,6‐diaminopurine chromophore. Evidence is presented that both are photostable compounds exhibiting similar deactivation mechanisms upon the population of the S1(ππ* La) state at 290 nm. The mechanism involves deactivation through the C2‐ and C6‐reaction coordinates and >99% of the excited state population decays through nonradiative pathways involving two conical intersections with the ground state. The radiative and nonradiative lifetimes are longer in aqueous solution compared to acetonitrile. Whileτ1is similar in both derivatives,τ2is ca. 1.5‐fold longer in 2,6‐diaminopurine‐2′‐deoxyribose due to a more efficient trapping in the S1(ππ* La) minimum. Therefore, 2,6‐diaminopurine could have accumulated in significant quantities during prebiotic times to be incorporated into non‐canonical RNA and play a significant role in its photoprotection.  more » « less
Award ID(s):
2246805
PAR ID:
10514686
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Wiley
Date Published:
Journal Name:
Photochemistry and Photobiology
Volume:
100
Issue:
2
ISSN:
0031-8655
Page Range / eLocation ID:
393 to 403
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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